Conventional multi-purpose tractors can be fitted with a variety of implements, e.g., dozer blades, snow plow blades, or bucket loaders. Because different implements often have different motion requirements, the hydraulics, underbody mounting brackets, and lift frame members associated therewith typically vary from implement to implement.
Movement of an implement is generally effected by hydraulic cylinders controlled by the operator from the cab or driver position of the tractor. Up and down motion is provided by a first pair of cylinders (generally referred to as lift cylinders); more precise motions, specific to the motion requirements of a particular implement, are provided by a second pair of cylinders. For example, a claw, digger or bucket loader may require up and down motion, provided by lift cylinders, and a pivot or "scooping" motion, provided by tilt cylinders. A snowplow, on the other hand, requires up and down motion, provided by lift cylinders and, ideally, a left to right sweeping motion pivoting about an axis perpendicular to the horizontal plane, provided by pivot cylinders.
If two implements sought to be interchanged have significantly different motion requirements, changing from one implement to the other can be quite cumbersome. Often the entire lift frame assembly, the underbody mounting brackets, and the associated hydraulic cylinders must be removed and replaced to accommodate the replacement implement's motion requirements.